No, if you take ephedra it won't cause you to lose muscle.
If you take ephedra and then run 2 miles a day expecting to lose fat, then yes, you will lose muscle from all that running.
If you take ephedra and eat 1500 calories a day expecting to lose a lot of fat, then yes, you will lose muscle from too low calories.
In short, you can do a lot of things while on ephedra that can cause you to lose a lot of muscle, but ephedra itself won't cause you to lose muscle. Do things right and you're fine.